Field of the Disclosure
The field of the disclosure relates to methods or devices used to dissect tissue during surgery or other medical procedures.
Technical Background
Surgeons frequently are required to sever or separate tissues during a surgical procedure. Two techniques are commonly used: (1) “sharp dissection” in which the surgeon uses a cutting instrument to slice a tissue, cutting with either scissors, a scalpel, electrosurgery, or other slicing instrument and (2) blunt dissection.
The advantage of sharp dissection is that the cutting instrument easily cuts through any tissue. The cut itself is indiscriminate, slicing through any and all tissues to which the instrument is applied. This is also the disadvantage of sharp dissection, especially when trying to isolate a first tissue without damaging it, when the first tissue is embedded in and obscured by a second tissue or, more commonly, in many tissues. Accidental cutting of a blood vessel, a nerve, or of the bowel, for example, is not an uncommon occurrence for even the most experienced surgeons and can lead to serious, even life-threatening, intra-operative complications and can have prolonged consequences for the patient.
Isolation of a first tissue that is embedded in other tissues is thus frequently performed by blunt dissection. In blunt dissection, a blunt instrument is used to force through a tissue, to force apart two tissues, or to otherwise separate tissues by tearing rather than cutting. Almost all surgeries require blunt dissection of tissues to expose target structures, such as blood vessels to be ligated or nerve bundles to be avoided. Examples in thoracic surgery include isolation of blood vessels during hilar dissection for lobectomy and exposure of lymph nodes.
Blunt dissection includes a range of maneuvers, including various ways to tear soft tissues, such as the insertion of blunt probes or instruments, inverted action (i.e., spreading) of forceps, and pulling of tissues with forceps or by rubbing with a “swab dissector” (e.g. surgical gauze held in a forceps). When needed, sharp dissection is used judiciously to cut tissues that resist tearing during blunt dissection.
The general goal is to tear or otherwise disrupt tissue, such as membranes and mesenteries, away from the target structure without tearing or disrupting either the target structure or critical structures such as nearby vessels or nerves. The surgeon capitalizes on the different mechanical behaviors of tissues, such as the different stiffness of adjacent tissues or the existence of planes of softer tissue between firmer tissues. Frequently, the goal is to isolate a target tissue that is mechanically firm, being composed of more tightly packed fibrous components, and is embedded in a tissue that is mechanically soft, being composed of more loosely packed fibrous components (for example, loose networks of collagen, reticulin, and elastin). More tightly packed fibrous tissues include tissues composed of tightly packed collagen and other fibrous connective tissues, usually having highly organized anisotropic distributions of fibrous components, often with hierarchical composition. Examples include blood vessels, nerve sheaths, muscles, fascia, bladders, and tendons. More loosely packed fibrous tissues have a much lower number of fibers per unit volume or are composed of less well organized materials such as fat and mesenteries. Fibrous components include fibers, fibrils, filaments, and other filamentous components. When a tissue is referred to as “fibrous”, the reference is typically to extracellular filamentous components, such as collagen and elastin—proteins that polymerize into linear structures of varying and diverse complexity to form the extracellular matrix. As mentioned in the previous paragraph, the density, orientation, and organization of fibrous components greatly determine the tissue's mechanical behavior. Sometimes, tissues are referred to as “tough, fibrous tissues” indicating that the fibrous or filamentous components are densely packed and comprise a significant fraction of the bulk of the tissue. However, all tissues are fibrous, to one extent or another, with fibers and other filamentous extracellular components being present in virtually every tissue.
What is important to the present discussion is that softer tissues tear more easily than firmer tissues, so blunt dissection attempts to proceed by exerting sufficient force to tear softer tissue but not firmer tissue.
Blunt dissection can be difficult and is often time-consuming. Judging the force to tear a soft tissue, but not a closely apposed firm tissue is not easy. Thus, blood vessels can be torn. Nerves can be stretched or torn. In response, surgeons attempt judicious sharp dissection, but blood vessels and nerves can be cut, especially a smaller side branch. This all leads to long, tedious dissections and increased risk of complications, like bleeding, air leaks from the lungs, and nerve damage.
Surgeons frequently use forceps for blunt dissection. FIGS. 1A and 1B show a typical forceps 10 of the prior art. FIG. 1A shows the forceps 10 in the closed position for clamping a tissue 34 between the opposing first clamp element 30 and second clamp element 31. FIG. 1B shows the forceps 10 in the open position, forcing tissue 34 apart. A first finger engager 20 and an opposing second finger engager 21 are used to actuate the mechanism. First finger engager 20 drives first clamp element 30, and second finger engager 21 drives second clamp element 31. A pivot 40 attaches the first clamp element 30 and the second clamp element 31, permitting a scissor-like action to force the first clamp element 30 and the second clamp element 31 together or apart, thereby clamping tissue 34 between the two clamp surfaces 35 and 36 or rending tissue 34 by the spreading of the first clamp element 30 and the second clamp element 31. Frequently, a ratcheting clasp 50 is used to lock the first clamp element 30 and the second clamp element 31 together.
Laparoscopic and thoracoscopic (collectively referred here as “endoscopic”) instruments use a similar action. FIG. 2 shows an example of an endoscopic forceps 110 of the prior art. A first finger engager 120 and an opposing second finger engager 121 are used to actuate the mechanism. First finger engager 120 is rigidly mounted to the instrument body 150. Second finger engager 121 drives opposing clamp elements 130 and 131. A pivot 140 attaches the two clamp elements 130 and 131, such that actuation of second finger engager 121 forces clamp elements 130 and 131 together, thereby clamping a tissue between two clamp surfaces 135 and 136. As in FIG. 1, endoscopic forceps 110 can be used to force a tissue apart. Clamp elements 130 and 131 are closed, inserted into a tissue, and then opened to tear the tissue.
For either instrument, forceps 10 or endoscopic forceps 110, a surgeon performs blunt dissection by closing the forceps, pushing the closed forceps into a tissue and then, optionally, opening the forceps inside the tissue, using the force applied by opening of the jaws of the forceps to tear the tissue apart. A surgeon thus proceeds to dissect a tissue by a combination of pushing into the tissue and opening the jaws of the forceps.
Blunt dissection is commonly used for wet and slick tissues, and the smooth, passive surfaces of most surgical instruments slide easily along the tissue, impairing the instrument's ability to gain purchase and separate the tissue. Furthermore, the surgeon has only limited control, being able only to jab, move sideways, or separate. An improved instrument for blunt dissection that could differentially separate soft tissues while not disrupting firm tissues would greatly facilitate many surgeries.